An evaporator coil is the indoor heat exchanger of an air conditioner or heat pump, usually mounted on top of the furnace or inside the air handler. In cooling mode, cold refrigerant evaporating inside the coil absorbs heat and moisture from the air blown across it. In heat pump heating mode, the same coil releases heat instead.
Why it matters to you
A dirty filter, closed vents or undersized return ducts starve the coil of airflow, which is the most common reason air conditioners freeze up on the first hot Fraser Valley days. Because a heat pump uses its coil year-round, keeping it clean matters more than on a summer-only AC.
Practical guidance
If ice appears on the coil or refrigerant lines, turn cooling off and leave the fan running to thaw it, and never chip the ice off. Change filters on schedule and have the coil cleaned during maintenance.